Dehydration-Driven Glass Formation in Aqueous Carbonates

Area of Science:

• Geochemistry
• Materials Science
• Biomineralization

Background:

• Amorphous carbonates (ACMC) are vital in biomineralization, volcanism, and deep carbon cycling.
• Anhydrous forms of amorphous calcium carbonate (ACC) and calcium-magnesium carbonate (ACMC) exhibit glass transition behavior.

Purpose of the Study:

• To investigate the influence of water content on the glass formation of ACC and ACMC.
• To develop a predictive model for the stability of amorphous carbonate phases.
• To explore dehydration-induced glass transitions for material processing.

Main Methods:

• Utilized novel fast differential scanning calorimetry (DSC) to study hydrous ACC and ACMC.
• Investigated the effect of varying water content on glass transition temperatures.
• Employed lyophilization as a method for isothermal dehydration and glass transition crossing.

Main Results:

• Demonstrated that water content significantly affects the glass formation of ACC and ACMC.
• Established a parametrization to predict the stability of amorphous carbonate liquid and solid phases based on temperature and water content.
• Confirmed that hydrous ACC and ACMC behave as structural glasses.

Conclusions:

• Dehydration-controlled formation of glassy ACC is a key intermediate step in the transformation to crystalline CaCO3 polymorphs.
• Lyophilization offers a viable route to controllably induce glass transitions in these materials.
• Findings have direct implications for understanding geological processes and biomineralization mechanisms.